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    A subquery is one query nested inside another query. The outer query uses the result of the inner query to filter, aggregate, or manipulate data. This makes subqueries powerful for handling complex database operations without breaking them into multiple separate queries.

    They can appear in SELECT, FROM, WHERE, or HAVING clauses and can be used with SELECT, INSERT, UPDATE, or DELETE statements.

    Example – Filtering with a Subquery in WHERE Clause

    SELECT NAME, LOCATION, PHONE_NUMBER
    FROM Student
    WHERE ROLL_NO IN (
    SELECT ROLL_NO
    FROM New_Student
    WHERE SECTION = 'A'
    );
    Cóipeáilte!

    Here, the inner query retrieves roll numbers of students in section 'A'. The outer query then fetches their details from the Student table.

    Types of Subqueries

    • Single-row subquery – returns exactly one value, often used with =, <, >

    SELECT * FROM Employees
    WHERE Salary = (SELECT MAX(Salary) FROM Employees);
    Cóipeáilte!

    • Multi-row subquery – returns multiple values, used with IN, ANY, ALL

    • Correlated subquery – depends on the outer query for values and runs once per row

    Why are subqueries important in SQL Server?
    They help us simplify the process of fetching data based on the result of another query which allows for more flexibility and efficiency in SQL statements. Whether you are calculating averages, filtering records or performing comparisons, subqueries are an essential tool in the SQL toolbox.
    geeksforgeeks.org
    LearnSQL.com
    https://learnsql.com/blog/sql-subquery-examples
    5 SQL Subquery Examples - LearnSQL.com
  1. GeeksForGeeks
    https://www.geeksforgeeks.org › sql › sql-subqueryAistrigh an toradh seo

    SQL Subquery - GeeksforGeeks

    22 Samh 2025 · This example demonstrates how to use a subquery inside the WHERE clause. The inner query retrieves roll numbers of students who belong to section 'A' and the outer query fetches their …

    • This example demonstrates how to use a subquery inside the WHERE clause. The inner query retrieves roll numbers of students who belong to section 'A' and the …

    Féach torthaí ó geeksforgeeks.org amháin
  2. LearnSQL.com
    https://learnsql.com › blog › sql-subquery-examplesAistrigh an toradh seo

    5 SQL Subquery Examples - LearnSQL.com

    • We’ll start with a simple example: We want to list paintings that are priced higher than the average. Basically, we want to get painting names along with the listed prices, but only for the ones that cost more than average. That means that we first need to find this average price; here’s where the scalar subquery comes into play: Our subquery is in...
    Féach tuilleadh ar learnsql.com
  3. Programiz
    https://www.programiz.com › sql › subqueryAistrigh an toradh seo

    SQL Subquery (With Examples) - Programiz

    SQL subqueries are queries inside another query. In this tutorial, you will learn about subqueries in SQL with the help of examples.

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  5. Dataquest
    https://www.dataquest.io › blog › sql-subquerie…Aistrigh an toradh seo

    SQL Subqueries: A Beginner’s Guide (with Code Examples)

    10 Meith 2022 · A subquery is nothing more than a query inside another query. …

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  6. w3resource
    https://www.w3resource.com › sql › subqueries …Aistrigh an toradh seo

    SQL Subqueries - w3resource

    13 Feabh 2025 · The SQL subquery is a SELECT query that is embedded in the main SELECT statement. The subquery can be nested inside a SELECT, INSERT, …

  7. DataCamp
    https://www.datacamp.com › tutorial › sql-subqueryAistrigh an toradh seo

    SQL Subquery: A Comprehensive Guide - DataCamp

    16 Ean 2025 · A SQL subquery is a nested query within another SQL statement used for complex data retrieval, filtering, and aggregation to enhance database queries.

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  9. KDnuggets
    https://www.kdnuggets.com › beginners-guide-subqueries-sqlAistrigh an toradh seo

    Beginner’s Guide to Subqueries in SQL - KDnuggets

    We’ve covered the four main subquery types and seen a practical example for each one. Take the fundamentals you got here to write your own SQL subqueries and suggestions on how to learn SQL to …

  10. Pickl.AI
    https://www.pickl.ai › blog › sql-subqueryAistrigh an toradh seo

    SQL Subquery with Examples - pickl.ai

    1 Aib 2025 · Subqueries help us find specific information from a database by using one query inside another. Let’s look at some real-world examples to understand …

  11. GeeksForGeeks
    https://www.geeksforgeeks.org › sql › how-to-use-a...Aistrigh an toradh seo

    How to Use a Subquery in a SELECT Statement - GeeksforGeeks

    23 Iúil 2025 · Subquery in a SELECT statement can be used to return a single value, multiple values or even a complete set of data depending on how it is structured. The most common type of subquery in …

  12. sqltutorial.net
    https://www.sqltutorial.net › subquery.htmlAistrigh an toradh seo

    Subquery – SQL Tutorial

    A subquery in SQL is a query that is nested within another query. It is used to retrieve data that will be used in the main query as a filter condition, or as a source of data for a calculation.

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